Plastic injection molded fans have been known for some time. See, for example, U.S. Pat. No. 4,569,632, which discloses a fan having back-skewed blades formed of a high-strength injection molded plastic. See also U.S. Pat. No. 4,358,245, which discloses an injection molded fan having blades that are highly forwardly skewed.
Typically, injection molded fans are produced by introducing molten plastic into a mold, and then opening the mold along a parting line to remove the cooled solid fan. The fan must be designed to permit removal from its mold.